The present invention relates to a derivative of .beta.-(4-isocyano-1,2,3,4-diepoxycyclopentyl)acrylic acid represented by the formula: ##STR1## and more in detail, the present invention relates to a derivative of the .beta.-substituted acrylic acid, the derivative being represented by the formula (I): ##STR2## wherein A represents
(1) --OR, wherein R is a residual group of an ester or ##STR3## wherein X and Y may be the same or different from each other and represent respectively a hydrogen atom or a group bonded to N, or X and Y may form a ring together with N. In the case where A represents ##STR4## in the formula (I), ##STR5## includes not only a group --NH.sub.2 but also an amino group having various substituting groups and a heterocyclic group including N, and in the case where A represents --OR in the formula (I), the R is a residual group of an ester, having various groups other than an alkyl group.
Previously, the present inventors found a new antibiotic substance, .beta.-(4-isocyano-1,2-3,4-diepoxycyclopentyl)acrylic acid (hereinafter referred to as the .beta.-substituted acrylic acid) in a cultured product of "No. 2188 production strain" (deposition number of the Fermentation Research Institute of Japanese Government: FERM P-142) of a mold belonging to Penicillium, producing an antibiotic substance, which had been isolated from soil. The antibiotic substance is disclosed in Japanese Patent Applications Laying-Open No. 59-17989 and No. 59-25398.
Thereafter, as a result of the present inventors' studies on the pharmaceutically improved derivatives of the .beta.-substituted acrylic acid, the present inventors have found that the esters of .beta.-substituted acrylic acid, a hydroxysuccinimide-derivative of .beta.-substituted acrylic acid and the acid amide of .beta.-substituted acrylic acid show antibacterial activity, antifungal activity and antimycoplasmal activity and have attained the present invention.